#94 Added CAST function support (#96)

* #94 Added CAST function support

Co-authored-by: Anastasiia Sergienko <anastasiia.sergienko@exasol.com>

doc/changes/changelog.md

@@ -1,5 +1,6 @@
 # Changes
 
+* [4.3.0](changes_4.3.0.md)
 * [4.2.0](changes_4.2.0.md)
 * [4.1.0](changes_4.1.0.md)
 * [4.0.0](changes_4.0.0.md)

doc/changes/changes_4.3.0.md

@@ -0,0 +1,7 @@
+# SQL Statement Builder 4.3.0, released 2020-10-22
+
+Code Name: CAST function support
+
+## Features / Enhancements
+
+* #94: Added CAST function support

pom.xml

@@ -4,7 +4,7 @@
     <modelVersion>4.0.0</modelVersion>
     <groupId>com.exasol</groupId>
     <artifactId>sql-statement-builder</artifactId>
-    <version>4.2.0</version>
+    <version>4.3.0</version>
     <name>Exasol SQL Statement Builder</name>
     <description>This module provides a Builder for SQL statements that helps creating the correct structure and
         validates variable parts of the statements.

src/main/java/com/exasol/sql/dql/select/Select.java

@@ -55,7 +55,7 @@ public Select field(final String... names) {
     /**
      * Add a function.
      * 
-     * @param functionName     a name of function
+     * @param functionName     name of function
      * @param valueExpressions zero or more value expression
      * @return <code>this</code> instance for fluent programming
      */
@@ -79,6 +79,30 @@ public Select function(final FunctionName functionName, final String derivedColu
         return this;
     }
 
+    /**
+     * Add a function.
+     *
+     * @param function          function
+     * @param derivedColumnName name under which you can refer to the derived column
+     * @return <code>this</code> instance for fluent programming
+     */
+    public Select function(final Function function, final String derivedColumnName) {
+        final DerivedColumn derivedColumn = new DerivedColumn(this, function, derivedColumnName);
+        this.derivedColumns.add(derivedColumn);
+        return this;
+    }
+
+    /**
+     * Add a function.
+     *
+     * @param function function
+     * @return <code>this</code> instance for fluent programming
+     */
+    public Select function(final Function function) {
+        function(function, "");
+        return this;
+    }
+
     /**
      * Add a User Defined Function.
      *

src/main/java/com/exasol/sql/expression/ValueExpressionVisitor.java

@@ -1,6 +1,7 @@
 package com.exasol.sql.expression;
 
 import com.exasol.sql.UnnamedPlaceholder;
+import com.exasol.sql.expression.function.exasol.CastExasolFunction;
 import com.exasol.sql.expression.function.exasol.ExasolFunction;
 import com.exasol.sql.expression.function.exasol.ExasolUdf;
 
@@ -41,4 +42,6 @@ public interface ValueExpressionVisitor {
     public void visit(NullLiteral nullLiteral);
 
     public void visit(BooleanExpression booleanExpression);
+
+    public void visit(CastExasolFunction castFunction);
 }

src/main/java/com/exasol/sql/expression/function/exasol/CastExasolFunction.java

@@ -0,0 +1,63 @@
+package com.exasol.sql.expression.function.exasol;
+
+import java.util.List;
+
+import com.exasol.datatype.type.DataType;
+import com.exasol.sql.expression.ValueExpression;
+import com.exasol.sql.expression.ValueExpressionVisitor;
+import com.exasol.sql.expression.function.FunctionName;
+
+/**
+ * This class represents the Exasol CAST function.
+ */
+public class CastExasolFunction extends ExasolFunction {
+    private final DataType type;
+
+    private CastExasolFunction(final ValueExpression value, final DataType type) {
+        super(ExasolScalarFunctionCast.CAST, List.of(value));
+        this.type = type;
+    }
+
+    /**
+     * Create a new {@link CastExasolFunction} instance.
+     *
+     * @param valueExpression value to cast
+     * @param type            type to cast the value to
+     * @return new {@link CastExasolFunction}
+     */
+    public static CastExasolFunction of(final ValueExpression valueExpression, final DataType type) {
+        return new CastExasolFunction(valueExpression, type);
+    }
+
+    /**
+     * Get the value to cast.
+     * 
+     * @return value to cast
+     */
+    public ValueExpression getValue() {
+        return this.valueExpressions.get(0);
+    }
+
+    /**
+     * Get the type to cast the value to.
+     * 
+     * @return type to cast the value to
+     */
+    public DataType getType() {
+        return this.type;
+    }
+
+    @Override
+    public boolean hasParenthesis() {
+        return true;
+    }
+
+    @Override
+    public void accept(final ValueExpressionVisitor visitor) {
+        visitor.visit(this);
+    }
+
+    private enum ExasolScalarFunctionCast implements FunctionName {
+        CAST
+    }
+}

src/main/java/com/exasol/sql/expression/function/exasol/ExasolAnalyticFunctions.java → src/main/java/com/exasol/sql/expression/function/exasol/ExasolAnalyticFunction.java

@@ -14,6 +14,6 @@
  * <a href="https://github.com/exasol/sql-statement-builder/issues/72"> github issue # 72</a>.
  * </p>
  */
-public enum ExasolAnalyticFunctions implements FunctionName {
+public enum ExasolAnalyticFunction implements FunctionName {
     ANY, EVERY, LISTAGG
 }

src/main/java/com/exasol/sql/expression/function/exasol/ExasolFunction.java

@@ -1,6 +1,8 @@
 package com.exasol.sql.expression.function.exasol;
 
-import java.util.*;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
 
 import com.exasol.sql.expression.ValueExpression;
 import com.exasol.sql.expression.ValueExpressionVisitor;
@@ -14,7 +16,7 @@ public class ExasolFunction extends AbstractFunction {
     private static final List<String> functionsWithoutParenthesis = Arrays.asList("SYSDATE", "CURRENT_SCHEMA",
             "CURRENT_SESSION", "CURRENT_STATEMENT", "CURRENT_USER", "ROWNUM", "ROWID", "SCOPE_USER", "USER");
 
-    private ExasolFunction(final FunctionName functionName, final List<ValueExpression> valueExpressions) {
+    protected ExasolFunction(final FunctionName functionName, final List<ValueExpression> valueExpressions) {
         super(functionName.toString(), valueExpressions);
     }
 
@@ -31,7 +33,7 @@ public static ExasolFunction of(final FunctionName functionName) {
     /**
      * Create a new {@link ExasolFunction} instance.
      *
-     * @param functionName name of the function
+     * @param functionName     name of the function
      * @param valueExpressions zero or more value expressions
      * @return new {@link ExasolFunction}
      */

src/main/java/com/exasol/sql/expression/rendering/ValueExpressionRenderer.java

@@ -1,9 +1,11 @@
 package com.exasol.sql.expression.rendering;
 
+import com.exasol.datatype.type.DataType;
 import com.exasol.sql.ColumnsDefinition;
 import com.exasol.sql.UnnamedPlaceholder;
 import com.exasol.sql.expression.*;
 import com.exasol.sql.expression.function.Function;
+import com.exasol.sql.expression.function.exasol.CastExasolFunction;
 import com.exasol.sql.expression.function.exasol.ExasolFunction;
 import com.exasol.sql.expression.function.exasol.ExasolUdf;
 import com.exasol.sql.rendering.ColumnsDefinitionRenderer;
@@ -55,7 +57,7 @@ public void visit(final FloatLiteral literal) {
     }
 
     @Override
-    public void visit(BigDecimalLiteral literal) {
+    public void visit(final BigDecimalLiteral literal) {
         appendCommaWhenNeeded(literal);
         append(literal.toString());
         setLastVisited(literal);
@@ -129,7 +131,7 @@ private void appendEmitsWhenNecessary(final ExasolUdf function) {
             appendKeyword(" EMITS");
             append(" ");
             final ColumnsDefinition columnsDefinition = function.getEmitsColumnsDefinition().get();
-            final ColumnsDefinitionRenderer columnsDefinitionRenderer = new ColumnsDefinitionRenderer(this.config);
+            final ColumnsDefinitionRenderer columnsDefinitionRenderer = getColumnsDefinitionRenderer();
             columnsDefinition.accept(columnsDefinitionRenderer);
             this.builder.append(columnsDefinitionRenderer.render());
         }
@@ -165,4 +167,21 @@ public void visit(final BooleanExpression booleanExpression) {
         booleanExpression.accept(expressionRenderer);
         append(expressionRenderer.render());
     }
+
+    @Override
+    public void visit(final CastExasolFunction castFunction) {
+        appendKeyword("CAST");
+        startParenthesis();
+        castFunction.getValue().accept(this);
+        appendKeyword(" AS");
+        final DataType type = castFunction.getType();
+        final ColumnsDefinitionRenderer columnsDefinitionRenderer = getColumnsDefinitionRenderer();
+        type.accept(columnsDefinitionRenderer);
+        append(columnsDefinitionRenderer.render());
+        endParenthesis();
+    }
+
+    private ColumnsDefinitionRenderer getColumnsDefinitionRenderer() {
+        return new ColumnsDefinitionRenderer(this.config);
+    }
 }

src/test/java/com/exasol/sql/expression/function/exasol/CastExasolFunctionTest.java

@@ -0,0 +1,27 @@
+package com.exasol.sql.expression.function.exasol;
+
+import static com.exasol.hamcrest.SqlFragmentRenderResultMatcher.rendersTo;
+import static org.hamcrest.MatcherAssert.assertThat;
+
+import org.junit.jupiter.api.Test;
+
+import com.exasol.datatype.type.Varchar;
+import com.exasol.sql.StatementFactory;
+import com.exasol.sql.dql.select.Select;
+import com.exasol.sql.expression.NullLiteral;
+
+class CastExasolFunctionTest {
+    @Test
+    void testRendering() {
+        final Select select = StatementFactory.getInstance().select()
+                .function(CastExasolFunction.of(NullLiteral.nullLiteral(), new Varchar(254)));
+        assertThat(select, rendersTo("SELECT CAST(NULL AS VARCHAR(254))"));
+    }
+
+    @Test
+    void testRenderingWithName() {
+        final Select select = StatementFactory.getInstance().select()
+                .function(CastExasolFunction.of(NullLiteral.nullLiteral(), new Varchar(254)), "TEST");
+        assertThat(select, rendersTo("SELECT CAST(NULL AS VARCHAR(254)) TEST"));
+    }
+}

src/test/java/com/exasol/sql/expression/function/exasol/ExasolAnalyticFunctionTest.java

@@ -16,7 +16,7 @@ class ExasolAnalyticFunctionTest {
     void testAggregateFunctionCoalesce() {
         final Select select = StatementFactory.getInstance().select() //
                 .field("department") //
-                .function(ExasolAnalyticFunctions.ANY, " ANY_ ", BooleanTerm.lt(column("age"), integerLiteral(30)));
+                .function(ExasolAnalyticFunction.ANY, " ANY_ ", BooleanTerm.lt(column("age"), integerLiteral(30)));
         select.from().table("employee_table");
         select.groupBy(column("department"));
         assertThat(select,